IRS Form W-9 is a tax form used by employers to properly identify their employees. In order for employers to properly withhold taxes from an employee’s pay, they need the employee’s identification number.
Form W-9 provides an employer with that identification number. Businesses with employees need the W9 form to properly file their taxes. In some special cases, such as if you are an independent contractor, your client may request a W-9 from you to report how much they paid you.